Detection of rock joints and opening degrees based on drilling parameters and moving average filter

2The joint opening degree is a critical index for assessing the stability of jointed rock masses, which directly impacts the rock mass quality. It is also a key factor influencing the design of tunnel support structures. Hammer and rotary drilling rigs, commonly employed as rock-breaking equipment in tunneling, inevitably encounter joints with varying opening degrees during construction. This research aims to enhance the sampling frequency of hammer and rotary drilling rigs and optimize the joint detection algorithm, thereby equipping these rigs with the capability to detect joint opening degrees. This paper develops high-frequency acquisition equipment for drilling parameters to realize millimeter-level data acquisition. Drilling experiments on jointed rock mass are conducted under conditions corresponding to joint opening degrees of 1 mm, 3 mm, and 5 mm. The relationships among joint opening degree, drilling parameters, and width of rock failure region are investigated. A joint opening degree detection algorithm is proposed based on the drilling parameters and moving average filter. The results indicate that the curves of penetration velocity and rotary pressure along the drilling direction exhibit a three-segment distribution, i.e. "stable segment - adjustment segment - stable segment". The variation curves of drilling parameters display a “velocity mountain” and a “pressure valley” in the failure region. The relative errors in joint opening degree estimation based on penetration velocity and rotary pressure range from 3.4% to 32% and from 6% to 35%, with average relative errors of 12.95% and 16.24%, respectively. • Developed a high-frequency acquisition equipment for drilling parameters (GTC100G-FC). • The curves of penetration velocity and rotary pressure along the drilling direction are distributed in three sections. • A drilling process data filtering method is proposed to identity the joint opening degree.